1. Field of the Invention
The present invention generally relates to the manufacture of semiconductor devices, and more particularly, the present invention relates to a method and apparatus for cleaning a semiconductor substrate.
2. Description of the Related Art
Subsequent to the completion of certain processes in the manufacture of semiconductor devices, it is necessary to clean the surface of a semiconductor wafer or substrate prior to proceeding to a next process. One such process which necessitates cleaning is the patterning of a metal film formed over the surface of the wafer. Here, a mask pattern is applied to a metal film, such as a tungsten or aluminum film, and the resultant is subjected to dry etching to remove portions of the metal film not covered by the mask, thus achieving a corresponding metal film pattern. After this process, the after must be cleaned to remove etch residues and metal polymers which may have formed at surfaces of the patterned metal.
Typically, the wafer is cleaned by dipping the wafer into a wet bath containing an organic stripping solution. An example of one such solution is the mixture of diglycolamine (DGA), hydroxylamine (HA), catechol, and water, at a ratio 60:16:5:19. In this example, DGA is an organic solvent, catechol is an additive, and HA is an amine-based reducing agent. The amine-based reducing agent functions to remove the metal polymers by breaking the linkages between the metallic polymer chains, and the organic solvent functions to dissolve the thus broken metallic polymer chains.
However, stripping solutions containing amine-based reducing agents such as HA do a poor job of removing metal-polymers containing a large quantity of oxygen and silicon. As such, stripping solutions containing fluorine, such as hydrofluoric acid (HF) have recently been developed in an effort to enhance the stripping solution's ability to remove metal-polymers and the etch residues.
Unfortunately, while stripping solutions containing fluorine do achieve improved removal of the metal polymers and etch residues, they also disadvantageously etch away at the thin dielectric layer underlying the metal pattern film layer. This is because the thin dielectric layer, such as BPSG, is easily etched when exposed to chemical solutions containing fluorine. Excessive etching of the thin dielectric can adversely affect device performance and yields. Accordingly, when using stripping solutions containing fluorine, there is a tradeoff between the effective removal of metal polymers and the undesired etching of the underlying thin dielectric.